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UC-NRLF 




DSS 



f 



REESE LIBRARY 

<)! 'I in: 

UNIVERSITY OF CALIFORNIA. 



Accessions No. 



. Class No. 



SMOKELESS POWDEK 



AND 



ITS INFLUENCE ON 

GUN CONSTRUCTION. 



BY 



JAMES ATKINSON LONGRIDGE, 

MEM. INST. CIVIL ENG. ; HON. MEM. OF NORTH OF ENGLAND INSTITUTE 

OP MINING AND MECHANICAL ENGINEERS ; 

AUTHOR OF <A TREATISE ON THE APPLICATION OF WIRE TO THE 

CONSTRUCTION OF ORDNANCE*; 'INTERNAL BALLISTICS,' 

ETC., ETC. 




E. & F. N. SPON, 125, STBAND, LONDON. 

NEW YORK: 12, CORTLANDT STREET. 

1890. 



Price 3s. 



REESE LIBRARY 



OF THE 



UNIVERSITY OF CALIFORNIA. 



^Heceived , i8g . 

| ; 

^Accessions No..... Class No..... ..... t 



SMOKELESS POWDER 



AND 



ITS INFLUENCE ON 

GUN CONSTEUCTION. 



IV BE 




SMOKELESS POWDER 



AND 



ITS INFLUENCE ON 

GUN CONSTRUCTION 



BY 



JAMES ATKINSON LONGRIDGE, 

MEM. INST. CIVIL ENG. ; HON. MEM. OF NORTH OF ENGLAND INSTITUTE 

OF MINING AND MECHANICAL ENGINEERS; 

AUTHOR OF 'A TREATISE ON THE APPLICATION OF WIRE TO THE 

CONSTRUCTION OF ORDNANCE'; 'INTERNAL BALLISTICS,' 

ETC., ETC. 




E. & F. N. SPON, 125, STRAND, LONDON. 

NEW YORK : 12, CORTLANDT STREET, 
1890. 



V 




IN the last chapter of my recent treatise on * Internal 
Ballistics' I alluded to the new powders which were then 
attracting the attention of artillerists. 

Keferring to their probable nature, I observed that the 
introduction of any ingredients which would either increase 
the volume of gas or its temperature, or both together, 
would not only explain the apparently anomalous action of 
these new powders, but probably result in the discovery of a 
still more powerful agent. 

Since then this has apparently been accomplished, and the 
old charcoal powder appears to be doomed to yield to this 
more powerful rival. 

But the adoption of this rival, whose properties are as yet 
only imperfectly known, is not to be viewed without anxiety. 
Can it be used with advantage, and above all with safety, in 
our new type forged steel guns ? If not, what changes will 
its use involve in gun construction ? What will be its effect 
as regards erosion ? How will it be affected by storage and 
change of climate ? 

These are important questions, to which I do not pretend to 
give complete answers, but I hope that the following remarks 
will be of some use in directing attention to the problems 
upon the solution of which future gun construction and 
ballistic practice largely depend. 

J. A. LONGKIDGE. 

GEEVE D'AZETTE, JERSEY. 
August 1890. 



CONTENTS 



I. INTRODUCTORY -. . . . . 1 

II. NATURE OF THE POWDER PRODUCTS OF COMBUS- 
TION POTENTIAL FORCE COMPARISON WITH 
OLD POWDERS . . . . , 4 

III. BALLISTIC EFFECT OF NEW POWDERS IN FRENCH 
AND GERMAN GUNS COMPARISON OF B.N. AND 
NOBEL'S POWDER 9 

IV. PRESSURES IN THE CHASE WITH NEW POWDER 
COMPARISON WITH PRESSURES FROM PEBBLE 
POWDER 17 

V. EFFECT OF THE NEW POWDER ON EXISTING GUNS . . 24 

VI. INFLUENCE OF THE NEW POWDER ON THE DESIGN 

OF GUNS 35 

VII. CONCLUSION 39 

APPENDICES 42 

POSTSCRIPT 49 





SMOKELESS POWDER. 



INTRODUCTORY. 

1. In few paths of science has the march of progress in 
the latter part of the nineteenth century been more remark- 
able than in the development of material for warfare. 

2. Less than half a century ago, the heaviest guns in our 
service were the old 68-pounders, weighing about five tons, 
and firing, with a charge of 20 Ibs. of powder, a spherical 
68 Ib. projectile to which it gave a velocity of about 1500 feet 
per second a ballistic effect equal to an energy of 1060 foot- 
tons. 

3. The heaviest service gun of the present day is the 
110-ton gun, firing a projectile of 1800 Ibs., with a charge of 
850 Ibs. of powder, and a velocity of 2100 feet per second, 
equivalent to an energy of 55,000 foot-tons. 

4. In the absence, in this country, of the definite know- 
ledge of the action and properties of powder (acquired through 
the researches of M. Sarrau. in France), the adaptation of 
the powder to the gun, and, vice versa, of the gun to the 
powder, has been a problem, the solution of which, so far 
as it has been solved, is of an empirical nature, so that the 
progress made in gun construction and powder manufacture 
has been of a somewhat erratic description. 

5. After the day of pebble powder came that of P 2 or 
C and C 2 , then that of prismatic, succeeded by that of 
brown cocoa, and finally that of the so-called E.X.E., which 

B 



2 SMOKELESS POWDER. 

a few months ago was looked upon as the ne plus ultra of 
gunpowder for heavy guns. 

6. The line taken by gunmakers has been tolerably con- 
sistent throughout. They have aimed at reducing the strength 
of the powder, keeping down the pressure, and making up for 
this by increased charges, enlarged powder chambers, and 
increased length of gun. 

Following out this line they have arrived at charges of 
one-half, or more, of the weight of the projectile, and at guns 
of 30 to 40 calibres in length, but with a maximum pressure 
limited to about 17 tons per square inch. 

7. In vain the argument has been urged that, by strengthen- 
ing the guns instead of weakening the powder, the same 
ballistic results could be obtained with greater convenience 
and less expense. It has been shown, both theoretically and 
practically, that wire guns can be made as safe under a 
pressure of 30 tons as forged steel guns under a pressure of 
17 tons ; but though a few experiments in this direction have 
been made at Woolwich, they have been made in a half- 
hearted way, extending over long intervals of time, daring 
which the construction of the type of* forged steel gun has 
been rapidly proceeded with, and may be said practically to 
include the whole of our new armament. 

8. These latter guns are designed specially for the use of 
such powders as the brown cocoa and E.X.E., that is to 
say, powder of which a very large charge is required. 

9. Until quite recently our artillerists have been in a 
happy frame of mind. They had got, or were very rapidly 
getting a sufficient supply of large guns of what they thought 
to be the best possible type, and they had the new E.X.E. 
powder, the best powder in the world. They had but to rest 
and be thankful. 

10. That rest has been of short duration. From Germany 
and France came rumours of a new powder giving wonder- 
ful ballistic results, and at the same time smokeless, or 
nearly so. 

11. Although much secrecy has been maintained with 



SMOKELESS POWDER. 3 

respect to the nature of the new powders, yet the results have 
been so far made public, that it is no longer doubtful that 
they will give ballistic results largely exceeding those obtained 
from cocoa and E.X.E., with considerably reduced charges 
and no excessive maximum pressure. 

12. This being so, the question arises, how far are our 
new type guns suited to the new powder, and to what extent 
shall we require a new armament, in order to reap the full 
advantage of the new powder ? It is proposed to discuss 
these questions by the light of such knowledge as the author 
can bring to bear upon the subject. 

13. This knowledge is too limited to enable him to produce 
a "treatise on the use of smokeless powder," but it may 
perhaps be useful in explaining in some degree the difference 
of action between the old and new powders, and the approxi- 
mate results obtained by the use of the latter, both as 
regards ballistic effect and the development of construction 
of guns suitable to its use. 

14. The subject is divided into the following parts : 
The nature of the new powder and the results of its de- 
composition as regards the volume of gas produced per unit 
of weight, the heat evolved, the temperature of combustion 
and a comparison with pebble powder, as a type of the old 
powders, the " Potential " and " Force " of the powder. 

An examination of the ballistic effects of the new powder 
in French and German guns. 

An inquiry into the pressures in the chase of Canet's 
15 cm. Q.F. gun, with B.N. powder, and a comparison with a 
full charge of pebble powder in the same gun. 

An examination into the effect of using the new ^powder 
in the existing new type forged steel gun. 

A few remarks on the influence of the new powder on the 
design of guns, and finally some general conclusions. 



B 2 



SMOKELESS POWDER. 



II. 

NATURE OF THE POWDER PRODUCTS OF COMBUSTION 
POTENTIAL FORCE COMPARISON WITH OLD POWDERS. 

15. The very remarkable results which have been recently 
obtained from smokeless powder in France and Germany, 
point to an entire revolution in artillery practice, as well as 
to a complete revision of the system of gun construction and 
the formulae of internal ballistics. 

16. M. Sarrau's formulae of velocity and pressure, which 
are very approximately correct for charcoal powders, such as 
the ordinary black and brown powders, are no longer appli- 
cable to the case of the new powders which give much higher 
velocities with smaller charges and reduced pressures. This 
must consequently lead to modifications in the proportions 
of guns, if it be admitted that these proportions are de- 
pendent on the pressures existing in different portions of the 
gun. 

17. The superior results obtained from the new powders 
are mainly due to the fact that, with them, nearly the whole 
of the powder is converted into permanent gases, whereas 
with the old powders only about 43 per cent, is so converted, 
the remaining 57 per cent, being inert matter existing in the 
gun in the form of a very finely diffused liquid, which, when 
cooled down, solidifies ; and is not only mainly the cause 
of the smoke, but also in all probability one cause of the 
excessive erosion. 

18. Although the chemical constitutions of the new 
powders are kept as secret as possible, they are probably all 
closely allied to that of Nobel's smokeless powder, that is to 
say, the main ingredients are nitre-cellulose and nitro- 
glycerine, to which is added nitrate or perchloride of 
ammonia and a little camphor. 




U IT 171 

'ELESS POWDER. 



SMOK 



19. An analysis of the reactions which take place on the 
explosion of this mixture is given in the Appendix A, and 
from this it appears that the whole of the products consist of 
permanent gases and watery vapour, the volume of which 
amounts to about 705 cubic centimetres for each gramme of 
powder. 

20. Further, that the heat evolved, after allowing for the 
vaporisation of the water, is about 1 7143 French units per 
gramme of powder. 

21. The mean specific heat of the products is found to be 
about -1989, and their theoretic temperature about 8673 C. 

22. Appendix B contains a similar examination of the 
results of combustion of pebble powder, which may be taken 
as a type of the old powders, from which it appears that the 
following are the results : 

Volume of gas from 1 gr. of powder .. 286 cm. cube. 

Gramme units of heat 690*2 

Mean specific heat -187 

Theoretic temperature of products .. 4:750 C. 

23. The temperatures above calculated may be called the 
" Theoretic or Potential Temperature." The actual tempera- 
tures are probably not more than one-half, owing partly to 
the cooling effect of the walls, and partly to the increase of 
the specific heat at the high temperature and pressure exist- 
ing in a gun ; but they probably represent the relative effect 
of the two powders as regards the temperature of the pro- 
ducts of combustion. 

24. The following comparison of the two powders may 
therefore be made : 





Pebble. 


Nobel's. 


Volume of gas at C. and '76 metres from 

TinwrlpT 


1 gramme ofi 


286 

690-2 
187 
4750 


705 

1714-8 
199 

8673C. 


Gramme units of heat evolved from 1 gramme 
Mean specific heat of products 


Theoretic temperature of products 






6 SMOKELESS POWDER. 

Potential of NobeTs Powder. 

25. By the " Potential " is meant the mechanical equiva- 
lent of the heat developed by the combustion of unit of 
weight of the powder, or E Q ; when Q is the quantity of 
heat evolved, E = 436 in French unities, or 772 in English 
unities. Now it has been shown that Q = 1*714 units per 
gramme, or 1714 per kilogramme. 

436 x 1714 
Therefore, Potential = iQOO = ^^ ' ^ me tre-tons 

per kilogramme, or 1095 foot-tons per Ib. of powder. 

26. In the treatise on ' Internal Ballistics ' * (page 8), 
there is a table of the " Potentials " of various explosives, 
and that of pebble powder is given as 460 foot-tons per Ib., 
or considerably less than the half of that of Nobel's powder ; 
but, as was there observed, the " Potential " of an explosive 
must not be confounded with the mechanical effect which 
may be obtained from it, nor with the pressure developed by 
its combustion in a closed vessel. 

27. At page 50, ' Internal Ballistics/ the symbol "/" was 
used to denote what is called by M. Sarrau, the " force " of 
the powder, and it was defined by the relation 

Po Vp TQ 

7 " 273 ' 

where p Q is the atmospheric pressure = 103 33 kilog. per 

square decimetre ; 

V Q is the volume of gases from unit of weight at tem- 
perature zero and atmospheric pressure ; 
T is the absolute temperature of combustion. 
Taking the kilogramme as unit of weight, the volume of 
gas is, for Nobel's powder, 705 x 1000 cm. 3 or 705 dm. 3 

If the actual temperature of combustion be taken as 
one-half of the theoretic value, or 4326 C., the absolute 
temperature 

= 4326 + 273 = 4599. 

* ' Internal Ballistics,' by J. A. Longridge. Spon, London, 1889. 



Therefore / = 



SMOKELESS POWDER. 
103-33 x 705 x4599 



273 

= 1,227,022 kilogrammes per square decimetre. 
The value of / for pebble powder is given at page 51, 
' Internal Ballistics,' as 263,600, consequently the ratio of/, 

1227022 

as between Nobel's powder and pebble, is = 4 655. 

Zoobuu 

28. The " force," /, as denned by M. Sarrau, is the abso- 
lute pressure of powder exploded in a close vessel entirely 
filled ; that is to say of gravimetric density = 1, and with 

ordinary powder p = f - - , where a is the proportion of 

non-gaseous matter, which, with ordinary powders, is about 
57 of the weight. In Nobel's powder a = 0, consequently 
p =/A and if A = 1, p =/= 1,227,022 = 122 '7 kilog, per 
mm. 2 = 78 '52 tons per square inch, which is nearly double 
that of pebble powder. 

29. It is therefore apparent that the Nobel powder is 
capable of producing much higher pressure than the pebble, 
and yet in practice it gives higher velocity with less 
charges and lower pressures. 

This apparent paradox is easily seen to be due to the 
absence of inert matter, the whole of the powder being con- 
verted into gas, instead of only 43 per cent, as in pebble 
powder, and the total volume of gas being 705 cm. 3 per 
gramme of powder, against 286 cm. 3 for pebble, whilst at 
the same time the temperature of combustion is about 
double. 

30. Actual Pressure in gun. The actual pressures in guns 
are of course much below the calculated values of p, for two 
reasons : first, because there is a loss of temperature due to 
the cooling action of the chamber walls, and secondly, 
because by the time the whole of the charge is burnt, the 
projectile has moved a considerable way along the chase 
and so increased the space to be filled by the evolved 



If, for instance, there be a maximum pressure of 15 tons in 



8 SMOKELESS POWDER. 

the gun (assuming for the moment that there is no loss of 
heat), we have 



and making 

p = 78-52, and p = 15, 

we get 

v = v x 3 506 ; 

so that, if the rate of burning of the powder were suitable, a 
full charge of gravimetric density = 1 might be fired, and 
yet the maximum pressure not exceed 15 tons per square 
inch, which would be attained when the projectile had moved 
3 ' 506 times the length of the charge along the chase. 

31. Another advantage will probably be the absence of 
fouling, as the whole of the matter is converted into gases, 
which leave little or no residuum in the gun. 

32. Erosion. As regards erosion, experience must decide. 
But it may be said that on the one hand, the products of 
combustion being entirely gaseous, instead of a mixture of 
gas and fluids, will probable erode less ; whilst on the other 
hand that the increased temperature and volume will tend 
to augment that erosion. 

With the new powder, the temperature no doubt falls 
more rapidly than with the ordinary powder, because the 
loss of heat being a function of the difference of temperature 
between the gases and the gun, is greater with high tempera- 
tures ; whilst on the other hand, with ordinary powder, it is 
quite possible that whilst the guns are expanding, heat is 
communicated to them from the highly heated liquid, arising 
from the non-gaseous portion of the charge diffused through 
them. The question of erosion must therefore be determined 
by experience. So far as our present knowledge goes, the 
smokeless powder in this respect appears to possess the 
advantage. 



SMOKELESS POWDER. 



III. 

BALLISTIC EFFECT OF NEW POWDERS IN FRENCH AND 
GERMAN GUNS COMPARISON OF B.N. AND NOBEL*S 
POWDER. 

33. Formulas for Pressure and Velocity. It is not surprising 
that the formulae which represent the ballistic action of the 
old powders are found to be inapplicable to the new powders, 
and although it is probable that M. Sarrau has already so 
modified his formula as to make it represent the action of 
the new powder, it is scarcely likely that the results of his 
investigations will be made public at present. 

34. Although the experimental data published are very 
limited, it will not be without interest to examine them care- 
fully. These data are contained in notices of results of 
firing, obtained at Essen in July and August 1889, with 
Nobel's powder fired from four different guns, and of the 
results obtained from the French B.N. powder fired from 
10 cm. and 15 cm. guns, or 3*937 and 5*90 inches calibre 
respectively. 

35. An examination of these results leads to a rather 
remarkable conclusion, which, however, must be taken with 
all reserve. 

It is as follows : 

1st. The muzzle velocity of the projectile is proportional to 
the f th power of the weight of charge. 

2nd. The maximum pressure in the gun is proportional to 
the square of the weight of the charge. 



(1) 
P = B w 2 . (2) 

The coefficients A and B are not constants, but are composed 



10 SMOKELESS POWDER. 

of various factors, which are functions of the form, dimension, 
and rate of burning of the grain in fact, what are called by 
M. Sarrau the " characteristics of the powder of the weight 
of the projectile, the calibre of the gun, and the length of 
travel of the projectile. 

In M. Sarrau's formula, he introduces another factor A, 
the gravimetric density, but this is in itself a function of the 
weight of charge, and of the calibre of the gun. 

Taking, for instance, M. Sarrau's monomial formula for 
velocity, as given at page 98, * Internal Ballistics/ 



where H is a factor containing the " force " and " charac- 
teristics " of the powder ; 

w = weight of charge ; 
A = gravimetric density ; 
I = length of travel of projectile ; 
W = weight of projectile ; 
c calibre of gun. 

Now, if X = equivalent length of chamber, 
weight of charge 



capacity of chamber 7854: c 2 A. 
substituting which in the above we get 



<^ 






and it is the part within the bracket that is represented by 
A in (1). 

In like manner Sarrau's formula for pressure is 



2 Aw'W* 
= K o" - 2 > 



SMOKELESS POWDER. 



11 



by substituting 



7854 



for A becomes 



1-75 



(4) 



and the part within the bracket represents the B in (2). 

36. From this it appears that in passing from the old to 
the new powders, the index of w is increased from f- to f in 
the expressions for velocity ; and from 1 75 to 2 in that for 
pressure, an increase which might be anticipated from the 
absence of inert matter in the products of combustion of the 
new powders. 

The coefficients A and B of course are different with dif- 
ferent guns, and different brands of powder. 

87. The results of the experiments made at Essen in 1889 
have been published in the ' Kevue d'Artillerie,' vol. xxxv. 
These experiments were made with Nobel's powder fired from 
four different guns, the details of which are given in the 
following Table, No. I. 

TABLE I. 





Number of Gun. 


I. 


II. 


III. 


IV. 

3-287 
40 
2310 
2-20 
to 
3-54 
15-5 
to 
17-84 


Calibre in inches 
Length of gun in calibres 
\Veight of gun Ibs 


1-968 
40 
490 
( 0-66 
to 
0-80 
3-81 
to 
4-10 


2-362 
40 
862 
0-66 
to 
1-21 
6-84 
to 
6-86 


2-984 
28 
904 
0-66 
to 
1-17 

I- 


of charge 
of projectile .. .. 



From the results obtained at Essen the following Tables 
II. and III. have been constructed. 

Table II. gives the value of the coefficients A and B of 
formula (1) and (2) ( 35). 

Table III. gives the velocities and pressures, calculated 



12 



SMOKELESS POWDER. 



with these coefficients employed in formulae (1) and (2), and 
compared with the results actually obtained at Essen. 



TABLE II. 



No. of 
Gun. 


Number 
of Rounds 
Fired. 


Size of 
Grain of 
Powder. 


Weight of 
Charge. 


Weight of 
Projectile. 


Coefficients. 


A. 


B. 






in. 


Ibs. 


Ibs. 






T 


/ ^ 


1378 


66 to '80 


3-81 


2560 


20-0 


X* 


I 5 


1181 


66 to -792 


4-10 


2455 


20-5 




/ 2 


1969 


1 to 1 20 


6-86 


1527 


5-79 





I 3 


1181 


1 to 1-10 


6-86 


1880 


10-20 


III. 


10 


1181 


66 to 1-17 


15 


1429 


10-20 




6 


1969 


2-2 to 3-74 


15-5 


879 


0-885 


TV 


4 


1557 


3-3 to 3-54 


17-84 


920 


1-215 


J. V 


2 


1181 


3-3 


17-84 


911 


1-215 




2 


1181 


3-286 


17-84 


986 


1-760 



TABLE III. 



No. of 
Gun. 


Eound . . 


1 


2 


3 


4 


5 


6 


7 


8 




VELOCITY Feet per 


Second. 








f Observed 


1886 


2089 


2171 


1798 


2014 


2070 






. 


[Calculated 


1887 


2104 


2165 


1797 


2018 


2077 








/ Observed 


1637 


1758 


1109 


1860 


2043 








. 


[Calculated 


1640 


1761 


1109 


1890 


2019 










/Observed 


1086 


1188 


1283 


1417 


1517 


1591 






. 


(Calculated 


1047 


1174 


1284 


1429 


1535 


1607 






TV 


| Observed 


1607 


1883 


2004 


2136 


2234 


2336 


2231 


2168 


JL V . 


(Calculated 


1588 


1821 


2044 


2151 


2259 


2364 


2231 


2166 




PRESSURES Tons per Square Inch. 




/Observed 


8'46 


8-96 


13-23 


9-72 11-33 


13-03 






I. 


(Calculated 


8-71 


11-83 


12-80 


8-94 12-16 


13-12 








("Observed 


6-89 


8-60 


3-12 


jf 


10-18 


12-48 






II. 


(Calculated 


7-00 


8-47 


3-10 


55 


10-20 


12-34 








/Observed 


5-76 


7-08 


8-60 


10-50 


12-35 


13-36 






III. 


(Calculated 


4-44 


6-65 


7-90 


10-20 


11-77 


13-96 








/Observed 


5-33 


8-43 


9-02 


9-25 


11-20 


11-69 


13-24 


14-35 


IV. 


(Calculated 


4-28 


6-17 


8-41 


9-63 


10-96 


12-30 


13-23 


14-40 



French Experiments. 

38. The experiments made with the French smokeless 
powder B.N. were made with two of Canet's quick firing 
guns of (10 cm.) 3 '937 inch and (15 cm.) 5 '905 inch calibre, 
each of 48 calibres in length. 



SMOKELESS POWDER. 



13 



This is the total length of gun over all, the length of 
travel of the projectile being about 38 calibres. 

The powders used were all of the description called B.N. 
In the 3-937 inch gun, three different lots were used, which 
may account for the difference of the coefficients A and B, 
whilst in the 5 905 inch gun the powder was of the same 
brand throughout. 

39. Table IV. gives the values of A -and B, and Table V. 
the comparison of the observed with the calculated ballistic 
results, corresponding with Tables II. and III. for the Nobel 
powder. 

TABLE IV. 



Gun 

Calibre. 


Number 
of Rounds 
Fired. 


Size of 
Grain 
unknown. 


Weight of 
Charge. 


Weight of 
Projectile. 


Coefficients. 


A. 


B. 


in. 






Ibs. 


Ibs. 






3-937 


6 


Lot 1 


5-28 to 8-58 


28-6 


526 


2314 




4 


Lot 2 


7-93 to 8-16 


28-6 


526 


2807 




5 


Lot 3 


7-93 to 9-92 


28-6 


470 


1847 


5-905 


9 


Lot 4 


17-64 to 33-08 


89-0 


198 


0172 



TABLE V. 



Gun. 


Round . . 


1 


2 


3 4 


5 


6 


7 


8 


9 








j j 






ins. 






VELOCITY feet per second. 


3-937 


/Observed 


1834 


2001 


2238 


2434 


2562 


2628 








Lot 1 


(Calculated 


1829 


2057 


2273 


2431 


2586 


2637 








3-937 


/Observed 


2490 


2555 


2582 


2559 












Lot 2 


\Calculated 


2482 


2574 


2591 


2540 












3-937 


/Observed 


2237 


2355 


2536 


2615 


2605 










Lot 3 


{Calculated 


2221 


2405 


2539 


2627 


2627 










5.Qf)fj 


/Observed 


1666 


1962 


2303 


2428 


2603 


2674 


2671 2750 


2746 


J7l/cl 


(Calculated 


1716 


2008 


2325 


2470 


2611 


2680 


2680,2750 


2750 




PRESSURES tons per square inch. 


3-937 


/Observed 


6-54 


8-79 


11-34 


14-20 


15-88 


16-83 








Lotl 


(Calculated 


6-45 


8-78 


11-47 


13-72 


16-17 


17-04 








3-937 


/Observed 


17-65 


17-97 


19-62 


18-16 












Lot 2 


(Calculated 


17-65 


19-47 


19-71 


18-73 












3-937 


/Observed 


11-75 


13-50 


16-64 


18-10 












Lot 3 


(Calculated 


11-62 


14-37 


16-60 


18-17 














/Observed 


4-13 


6-22 


11-77 


13-66 


16-76 


16-83 


17-34 


18-41 


18-54 


5-905 


(Calculated 


4-83 


8-36 


12-00 


14-18 


16-38 


17-56 


17-56 


18-81 


18-81 









14 SMOKELESS POWDER. 

40. From these tables it appears that the formulae (1) and 
(2), above given, represent very closely the results obtained 
by experiments, and it is therefore probable that the indices 
75 and 2 denote the relations between the weight of the 
charge and the velocity and pressure respectively, at any rate 
it is so in these guns. 

41. A comparison may be made between the French B.N. 
and the Nobel powder, first as regards the energy of the 
projectile per Ib. of powder, and second as regards the energy 
per ton weight of gun. 

For this purpose take the (10 cm.) 3 '937 inch Canet gun, 
weighing 4620 Ibs., and compare it with the 3*287 inch 
Krupp gun, weighing 2310 Ibs. ; the Canet gun being fired 
with B.N., and the Krupp gun with Nobel's powder of 1557 
inch size of grain. 

It is assumed that the strain on the two guns is the same, 
that is to say, that the charge shall be such as will give the 
same maximum pressure in the two guns, and that this 
pressure shall be 18 '17 tons per square inch, as in the fourth 
round of this gun in Table V., giving a velocity of 2615 foot- 
seconds. 

Therefore, in the Canet gun, 



which gives 

Energy per ton of gun 657*1 foot-tons, 
per Ib. of powder 136*7 foot-tons. 

42. In the 3*257 inch Krupp gun, in order to give the 
pressure of 18* 17 tons, the weight of charge of the * 1557 inch 
grain Nobel powder is found by the equation P = 1 215 w 2 , 
whence 



and the velocity with this charge would be 

V = 920 w" 75 = 2537 feet per second; 



SMOKELESS POWDEE. 



15 



therefore 



which gives 



foot-to,,, 



Energy per ton of gun = 771 7 foot-tons. 
per Ib. of powder = 205 8 

43. If the powder of 0*1969 inch grain were used, the 
requisite weight of charge would be 4*531 Ibs., and the 
velocity 2730 feet per second, giving the Energy of the 
15 Ib. projectile = 774*7 foot-tons, which gives 

Energy per ton of gun = 751*2 foot- tons. 
per Ib. of powder = 171 

44. These results are brought together for comparison in 
the following Table. 

TABLE VI. 





3-937 inch Gun. 
B.N. Powder. 


3-287 inch Gun. 
1557 inch 
Nobel. 


3 -287 inch Gun. 
1969 inch 
Nobel. 


Total energy 
Energy per ton of gun 
Energy per Ib. of powder . . 


1355 
657-1 
136-7 


795-8 
771-7 
205-8 


774-7 
751-2 
171-0 



45. The results show somewhat in favour of the Nobel 
powder, both per ton of gun and per pound of powder. 

46. It must further be observed that the 3 937 inch gun 
has the advantage over the 3 287 inch gun, in being a gun of 
48 calibres as against 40 calibres in the latter. If the guns 
had been what is termed " similar guns " and similarly 
loaded, the velocities would have been the same, but the 
weight of projectiles as the cubes of the calibres, con- 
sequently the energy of similar guns increases as the cube of 
the calibre, which in the present case is in the ratio 



'3-937\3 



,3-287; 



1-719. 



16 SMOKELESS POWDER. 

Consequently, had the guns been similar and similarly 
loaded, the total energy would have been 

as 1355 : 788-5; 

so that not only is the energy of the smaller gun greater than 
the due proportion, but this is the case under the disadvantage 
of being the shorter gun. 

47. So far then as these experiments go, it appears that 
the Nobel powder is superior in ballistic power to the B.N. 
powder. 



SMOKELESS POWDER. 17 



IV. 



PRESSURES IN THE CHASE WITH NEW POWDER COMPARISON 
WITH PRESSURES PROM PEBBLE POWDER. 

48. In the absence of further experimental' data it is 
impossible to deduce the relations between the velocity and 
pressure and the other ballistic elements, such as the length 
of travel of projectile, weight of projectile, and calibre of the 
gun, so that the coefficients A and B given above can only 
be made use of for " similar " guns. 

49. It is very important to ascertain as far as may be 
possible, the distribution of pressures along the chase whilst 
the projectile is travelling to the muzzle. 

50. As has already been shown, there is reason to believe 
that in a close vessel impermeable to heat, the pressure from 
the new powder would be about double of that given by the 
old black powder. Consequently, as in practice the maximum 
pressure is not greater, it follows that the rate of combustion 
must be slower, thus giving more time for the projectile to 
get out of the way, and by thus increasing the space, keep 
down the pressure. 

It is also quite possible that the combustion may go on for 
a considerable time after the maximum pressure is attained, 
and that thus the pressures towards the muzzle may be 
greater than with the ordinary powders. 

51. As this is a point of great importance relative to 
the designing of guns, the question requires examination, 
so far as the limited experience available enables it to be 
done. 

52. Consider the case of the (15 cm.) 5*905 inch Canet 

c 



18 SMOKELESS POWDER. 

Q.F. 15 cm. gun of 48 calibres with B.N. powder, of which 
the following are the ballistic elements : 

CANET'S Q.F. 15 CM. GUN. 

Calibre of gun ........ 5*905 inches. 

Length of travel of projectile .. 224*5 

Equivalent length of chamber .. 53 

Capacity of chamber ...... 1500 cubic inches. 

of chase ........ 6174 

Total capacity of gun ...... 7674 

rr/trr j 

Number cf expansions Z- = 5*116 
1500 

Weight of charge ........ 33*08 Ibs. 

Weight of projectile .. .. .. 89 

Weight of gun ........ 6*29 tons. 

Muzzle velocity ........ 2750 f.s. 



Total energy = 4665 foot-tons. 

Energy per ton of gun ...... 744' 6 

per Ib. powder ...... 141*0 , 

Maximum pressure ...... 18*81 tons per sq. in. 

53. First, it may be asked, what must have been the mean 
pressure in the gun ? The total energy expended on the 
projectile was 4665 foot-tons, to which must be added that 
expended in overcoming friction and expelling the gases, &c. 
This may be estimated at an additional 20 per cent, making 
the total energy 5598 foot-tons. 

Now the area of section of the projectile is 27*4 inches, and 
the travel 18*4 feet. Therefore, if p be the mean pressure, 

p = -- -- - = 10*92 tons per square inch. 

54. Next, if it be granted that the pressure in a close 
vessel would be 78 * 53 tons per square inch, and that the pro- 
ducts of combustion act as a perfect gas, it may be inquired, 
at what point in the travel of the projectile will the pressure 
be reduced to the maximum pressure of 18 * 81 tons ? This 
can only be approximately ascertained in the absence of 



SMOKELESS POWDEE. 19 

knowledge as to the loss of heat due to cooling, but from the 
considerations set forth in ' Internal Ballistics/ Chapter V., 
it would appear that this is not very great. Leaving this 

loss out of account, there is the relation ^ = ( ) , where 

p W 

PO and V Q are the original and p and v the final pressures and 
volumes, and as the volumes are proportional to the lengths, 

the relation becomes = (= ) . Now let 1 Q be the length 

of the bore which would be occupied by the charge at 
gravimetric density = 1, and I the distance from the breech 
at which the pressure is reduced to p = 18 '81, then 



4i9 



55. For ordinary powder the space occupied at gravimetric 
density = 1, is 27 7 cubic inches per Ib. or 1 decimetre cube 
per kilogramme, and when the charge is thus spaced it is said 
to be of gravimetric density equal unity. If, however, the 
space be any other number, say 30 inches to the Ib., the 
gravimetric density is said to be 



56. It is as well to observe, however, that, with the French, 
" densite gravimetrique " has a different meaning. 

" Densite gravimetrique "is the weight of 1 cubic deci- 
metre of powder, not pressed together except by its own weight. 
Consequently it is evident that the " densite gravimetrique " of 
a given powder is dependent partly on its absolute density, 
i. e. specific gravity, and partly on the size of the grain. For 
instance, the French powder F x has an absolute density of 
1 * 750, whilst its gravimetric density is 830 to 870, whilst 
the WJij-, which has nearly the same absolute density, has a 
gravimetric density of 1 03 to 1 17. 

The equivalent of " gravimetric density " in French is not 
" densite gravimetrique," but '* densite de chargement." 

c 2 



20 SMOKELESS POWDER. 

57. As is well known, with the ordinary old powders 27 7 
cubic inches is the space occupied by 1 Ib. of powder. But 
this is not so with the new powder. With respect to this there 
is much reticence. It is, however, probable that 1 Ib. of this 
powder may occupy about 31 cubic inches of space, and it is 
on this assumption that the following remarks are made. 
Though the conclusions arrived at may not be quite 
correct, yet they will be relatively so, and will therefore be 
useful in the examination of the ballistic properties of the 
new powder. 

58. Assuming, then, that the space occupied by 1 Ib. of 
powder is 31 inches, the length of bore 1 Q occupied by the 
charge is easily determined. 

The charge being 33*08 Ibs., and the area of the bore 
27 4 inches, we get 

_ 33-08 x 31 Q _ . 
Length = = 37-42 inches. 

59. Let, then, A D (Fig. 1) represent the bore of the gun* 
A B the " equivalent length " of the chamber, that is to say, 
a length of bore whose capacity is the same as that of the 
chamber, and B D the travel of the projectile, and let A A be 
the length of the bore which would be occupied by the 
charge at gravimetric density = 1, that is to say, in the 
present case 37 42 inches. Then, if the powder were fired in 
a close vessel, the pressure would be 78 53 tons per square 
inch ; but as the projectile moves away the space increases, 
and the contest between the evolution of gas and the increas- 
ing space goes on until a maximum pressure is reached. If 
it be assumed that all the powder is burnt at this time, the 
point Ci, on the curve F C x D, corresponding to this maximum 
pressure, will denote the position of the projectile, and the 
ordinates between C and D the respective pressures on the 
bore as the projectile moves to the muzzle ; the curve 
F G! D being calculated from the formula 

l-319 



SMOKELESS POWDER. 



21 



The ordinates between B and C* are indeterminate, and 
depend upon the rate of evolution of the gas, the weight of 
projectile and other elements, but it may be assumed that 
approximately the pressure curve is represented by the curve 
B G! D! D, and that the point of maximum pressure is at C 1? 



Tarts 
SO] 



70- 



60- 



50- 



40- 



JO 



20- 



S F 

1 18 -53 torus 



FIG. 1. 




and that the total work done on the projectile is represented 
by the area of the curve multiplied by the area of the bore 
of the gun. 

60. Taking the unit for abscissa in feet, and for the ordinate 
in tons per square inch, the area of the curves A GI D t D is 
found to be 210*2, which is the foot-tons per square inch of 



* The assumption that the curve from B to C t is one-fourth of an ellipse 
has been found by the author to give very satisfactory results. 



22 



SMOKELESS POWDER. 



bore; and multiplying this by 27*4 the area of the bore 
gives 5761 foot-tons. If from this be deducted 20 per cent, 
for the resistance, friction, and expulsion of the gases, there 
remains 4629 foot-tons for the energy of the projectile. 

This was found by experiment to be 4665 foot-tons. 

It may therefore be concluded that the pressure curve 
(Fig. 1) represents, approximately, the pressure in the gun 
with a 33 Ib. charge of the new powder. 

61. Let now this be compared with the corresponding 
diagram of the same gun fired with a full charge of pebble 
powder. 

The capacity of the chamber being 1500 cubic inches, the 
1500 



full charge will be 
Appendix C, gives 



27-7 



Muzzle velocity .. 
Pressure on projectile 



= 54 Ibs., which, as is shown in 



2570 feet per sec. 
22 -00 tons. 



Therefore the energy is 
2570 2 x 89 



x 2240 



= 4073 foot-tons, 



which gives 



Energy per ton of gun 
per Ib. of powder . . 



650 -2 foot-tons. 
75-43 



62. The following Table shows the comparison between 
the B.N. and pebble powders in the 5 * 90 inch gun. 



Powder. 


Weight 
of 
Charge. 


Weight 
of 
Projectile. 


Muzzle 
Velocity. 


Maximum 
Pressure 
on 
Projectile. 


Total 
Energy. 


Energy. 


Per Ton of 
Gun. 


Per Lb. of 
Powder. 




Ibs 


Ibs 


feet per 


tons per 


foot- 












second. 


sq. in. 


tons. 






B.N. 


33-08 


89 


2750 


18-81 


4665 


744-6 


141-0 


Pebble.. 


54-00 


89 


2570 


22-0 


4073 


650-2 


75*43 



SMOKELESS POWDEE. 



23 



63. If a pressure curve be constructed for the pebble 
powder in the same manner as above described, and super- 
imposed upon the curve for the charge of 33 08 Ibs. of B.N. 
as in Fig. 2, the difference in the distribution of pressure is 
very strikingly seen. 

FIG. 2. 




64. The maximum pressure on the base of the projectile 
is 18 * 81 tons per square inch with the B.N., and 22 tons with 
the pebble powder, but the position at which it attains its 
maximum is when the shot has travelled 59 inches in the 
first case, against 16 inches in the second. 

Again, the final pressure is 5 65 tons per square inch with 
the B.N., against 3 1 tons with the pebble powder. 



24 SMOKELESS POWDER. 



V. 

EFFECT OF THE NEW POWDER ON EXISTING GUNS. 

65. Enough has now been said to show that the new 
powder is a revolutionary element in ballistic practice, and 
that it must consequently exert a corresponding influence 
on gun construction. 

66. It is therefore very important to examine what will be 
the effect of using such powder in the present new type steel 
guns, which were designed for the older powders, such as the 
black and brown prismatic, and the still later E.X.E. powder. 

67. These powders are characteristically weak powders, 
that is to say, they burn slowly and give low pressures in 
guns. The effect is made up by largely increasing the 
charges, and in order to give time for the entire combustion 
and also for utilising the expansive force of the gases, the 
guns are made very long. 

In order to contain the large charges and also to reduce 
the length of the gun, enlarged powder chambers are 
adopted, with, however, the disadvantage of increasing the 
size of the breech mechanism, and the strain upon it. 

68. Now, in the first place, it may be asked what will be 
the effect of using the new powders on these guns ? It is 
claimed for the new powders that, in addition to their quality 
of smokelessness, they will give vastly higher ballistic 
results, while they will strain the gun less owing to their 
low maximum pressure, and this statement has been used 
as an argument against the necessity of adopting wire 
guns, instead of the usual forged steel construction. 

68a. It is not intended to enter here into the questions of 
the relative cost of production, the greater freedom from 



SMOKELESS POWDER. 25 

latent defects, the quicker production, or the relative facilities 
of repairs, in all which respects the wire system has 
undoubted advantages. But it is desired to show that, if 
the full advantage is to be obtained from the high ballistic 
properties of the new powder, it can only be obtained by the 
use of comparatively high pressure, and consequently, very 
strong guns, such as can only be produced by the wire system 
of construction. 

69. It is argued that the advantages of the new powders 
may be utilised in two ways. 

70. Either by retaining the present initial velocity with 
the benefit of a great reduction of pressure, or on the other 
hand by retaining the present maximum pressure of about 
16 tons per square inch, and thus obtaining a very great 
increase of velocity, although admittedly retaining the 
disadvantage of a great length of gun. 

71. The former alternative is thought to be the better 
for field guns, as they cannot be lengthened without increase 
of weight, which is inadmissible. Morever, the weight of 
cartridges could thus be reduced, consequently more of them 
could be carried ; whilst it has also been said that, as the 
pressures are reduced, the strain on the gun carriage would 
be relieved. 

72. This last assertion is, however, a mistake. The effect of 
the strain on the carriage is proportional to the work done 
on it, and this varies as the square of the velocity of recoil, 
which velocity, cseteris paribus, is in proportion to the 
velocity of the projectile, and has nothing to do with the 
pressure by which that velocity is created. 

Consequently, if the muzzle velocity be unchanged the 
strain on the carriage must be the same, and if, by the use 
of the new powder, the velocity be increased, the strain on the 
carriage must be increased correspondingly. 

73. This is of course slightly modified by the fact that, in 
calculating the velocity of recoil, a portion of the weight of 
the charge must be taken into account, as well as the weight 
of the projectile, but the effect of this will be comparatively 



26 SMOKELESS POWDER. 

small, and in the case of increased velocity of the projectile, 
will be far less than the increase due to the increased 
velocity of the projectile, which is not a function of the 
maximum pressure, but depends on the mean pressure, which 
is quite another thing. 

74. As regards the length of gun required for the new 
powder, it is argued that by increasing the pressure it would 
be necessary also to increase the length of the gun to a 
practically impossible extent. 

75. But this also is erroneous, for it apparently rests on 
the assumption that the maximum pressure can only be 
increased by increasing the weight of charge, and that unless 
the length of the chase be correspondingly increased, part 
of the charge will be blown out of the muzzle unburnt. 

76. Now the maximum pressure depends, not altogether, 
nor indeed principally, on the weight of the charge, but is 
chiefly affected by the rate of evolution of the gas, which 
is regulated almost ad libitum by modifying the form and 
size of the grain. 

It is therefore quite practicable to increase the maxi- 
mum pressure, even if the weight of charge be diminished. 

77. This will be the more evident after the following 
examination of the action of the powder in a gun. 

78. In the first place, reverting to Fig. 2 which shows 
the pressure in the same gun when fired with charges of 
33*08 B.N. and 54 Ibs. P respectively; in order to complete 
the curves the pressures behind the points of the maximum 
must be indicated. 

79. According to M. Sarrau's formulae for ordinary powder, 
if P be the pressure on the breech, P the maximum 
pressure on the base of the projectile, making use of Eng- 
lish unities of pounds for weight and tons per square inch 
for pressure, 



w and W being the respective weights of charge and projectile. 



SMOKELESS POWDEE. 27 

Another formula which is said to give better results, 
especially with slow powders, is 



_ P 
" 



80. Making use of this latter formula and the weights 
corresponding to Fig. 2, we find 

For B.N. powder P = P 1^ = 1 19 P. 

Oi7 



For pebble P = P = 1-30 P. 

by 

From which the breech pressures corresponding to the 
maxima in the diagrams are 22 -38 and 28 -6 tons respec- 
tively. 

Setting off these ordinates at the breech the line C^ 
represents the internal pressure in the gun when the pro- 
jectile is at Cj, and a line parallel to it, such as g g^ represents 
the pressure when the projectile is at any other part g. 

81. What is most important to note is that whilst the 
maximum pressure is considerably less with the B.N. powder, 
although the work done is nearly 15 per cent, more, and 
the powder charges 40 per cent, less, the pressures are 
thrown so much further forward, that the B.N. powder if 
fully utilised will require a very differently proportioned 
gun, one, namely, in which there is about the same strength 
behind the point of maximum pressure, but very much 
greater strength in front of it. 

82. Taking for instance the point g lt Fig. 2, at 110 inches 
from the muzzle, the pressure to be resisted will be 10 tons 
per square inch with the B.K powder, as against 5 J tons with 
the pebble. 

83. It is quite true that this pressure may be reduced by 
reducing the charge of the B.N. powder. 

84. If, instead of firing with 33 * 08 Ibs., the charge was 
reduced to 28 f 52 Ibs., the velocity would be the same as 
that given by the 54 Ibs. of pebble powder, and the maximum 



28 



SMOKELESS POWDEE. 



pressure would be reduced to 14 tons per square inch. The 
length of charge would be 30 inches of the bore. 

85. The dotted curve, Fig. 3, is constructed from these 
data, and being superimposed on the diagram for 54 Ibs. of 
pebble powder, shows the respective action of the two 

FIG. 3. 



28 54 B.N 
54-CC P 




-53 ; 



224-- 5 - 



powders in the same gun, while producing the same ballistic 
effects. 

86. It is evident that a gun designed to sustain the 
pressures of the pebble powder is insufficient in strength to 
sustain the pressures of the new powder in all that part of 
the chase commencing at about 180 inches from the 
muzzle. 

87. To elucidate this, let an examination be made of the 
Eoyal Gun Factory 6 a B.L. gun, MAKK IV. of the follow- 
ing ballistic elements : 



Calibre 

Length of rifling .. 
Capacity of chamber 
Equivalent length of ditto 
Total capacity of gun .. 

Expansions 

Charge E.X.E 

Weight of projectile 
Muzzle velocity 
Maximum pressure 



6 inches. 
127 

1364 cube inches. 
47-03 inches. 
5105 cube inches. 
3-743. 
48 Ibs. 
100. 

1980 feet per second. 
16 % 50 tons per sq. in. 



SMOKELESS POWDEE. 



29 



88. In order to compare this gun with the 15 cm. Canet 
gun, it must first be considered on the supposition that it is 
lengthened so as to make the travel of the shot the same, 
viz. 224*5 inches, and then determined what would be the 
muzzle velocity with the same charge of 48 Ibs. of E.X.E. 
powder but with a projectile of 89 Ibs. 

89. From such data as are at the author's disposal it 
appears that the " characteristics " of the E.X.E. powder 

are 

Log a = -06136 
Log/3 = - 1-47844 

Making use of which in Sarrau's binomial formulae for 

velocity gives 

V = 2444 feet per second. 

90. This is the velocity which is taken as a basis of com- 
parison with the Canet gun fired with B.N. powder. 

Now, by formula (1) 

V = 198 to*, 

and making V = 2441 gives 

w = 28 -52 Ibs. 

Then by formula (2) 

P = -0172w; 2 , 
which making w = 28 52 gives 

P = 14 tons per sq. inch 

for the Canet gun. 

The comparison is therefore as follows : 





Charge. 


Projectile. 


Muzzle 
Velocity. 


Maximum 
Pressure. 




Ibs. 


Ibs. 


feet per 
second. 


tons. 


Canet 15 cm. gun .. 


28 -52 B.N. 


89 


2444 


14 


R.G.F. 6 in. Mark IV.) 
lengthened / 


48 E.X.E. 


89 


2444 


16-5 



30 



SMOKELESS POWDER. 



Thus, with 2J tons less pressure the Canet gun only 
requires about T 7 ^ of the charge required of E.X.E. 

91. It remains, however, to be seen how the variations of 
pressure throughout the chase take place in the two guns, 
and for this purpose recourse must be had to pressure curves, 
obtained as above described. These, though not accurately 
correct, represent approximately the real pressures. The 
curve for the E.X.E. powder is obtained by making use of 
the formula given in 'Internal Ballistics,' page 172, with 

FIG. 4. 




allowance of 20 per cent, for resistance, and is represented by 
the full line in Fig. 4. 

92. The curve for the B.N. powder is obtained as follows : 
The charge of 28-5 Ibs. at gravimetric density = 1 would 
occupy 28-5 x 31 = 883 cubic inches, which is equal to 
30 inches of- the bore, and the initial pressure in this space 
would be 78-52 tons per square inch. Therefore the equa- 
tion to the curve is 

/30 

= 78-52 



from which the curve represented by the dotted line, Fig. 4, 
is constructed. 

Placing the two curves over each other, as shown in the 



SMOKELESS POWDEE. 31 

figure, it is seen that, although the maximum pressure of the 
B.N. powder is 3 tons less than that of the E.X.E., yet it is 
thrown about 39 inches further forward, and that at this 
point the pressure is about 4 tons per square inch greater 
than it is with the E.X.E. at the same point in the gun. 

93. To pass from this to the Mark IV. gun of the actual 
length, it is sufficient to cut off from the diagram the excess 
of length in front of A ; the length up to A being that of 
the travel of the shot with Mark IV. gun, viz. 127 inches. 
Then, by subtracting the areas A A! G! C and A A 2 C 2 C from 
the original areas of the two curves, the remaining areas 
represent the work done in the two guns if reduced to the 
length of the actual Mark IV. gun. 

The original areas are 4537 for each, and the deductions 
1299 and 1032; therefore the remaining areas are 3238 and 
3505 respectively, representing the energies of the two guns 
corresponding to muzzle velocities of 2049 and 2132 feet 
per second. 

94. From this it follows that with the E.G.F. 6-inch 
Mark IV. gun and a projectile of 89 Ibs. nearly the same 
velocity would be obtained from 28^ Ibs. of B.N. as from 
48 Ibs. of E.X.E., and that with 3 tons per square inch less 
maximum pressure. But this maximum would be about 
39 inches nearer the muzzle. 

95. Let it now be inquired how the new distribution of 
pressure would affect the Mark IV. gun ? 

It may be assumed that this gun has no superfluous 
strength, especially in front of the trunnions ; indeed, 
evidence is not wanting to show that the strength of existing 
guns is deficient rather than excessive in this respect. 

But let it be assumed that the present strength is suitable 
for the pressures developed by a full charge of 48 Ibs. E.X.E. 
powder. 

96. Let the strength of the gun be examined at two points, 
one at 64 inches, the other at 32 inches from the muzzle. 
At the first point the gun consists of the A tube 1 75 inch 
thick, and the B l tube 1 '385 inch thick. 

, 




32 SMOKELESS POWDER. 

At the second point it consists of the A tube, 1 * 35 inch 
thick, and the BX tube, 1'25 inch thick. 

97. According to the principles laid down in the Official 
Treatise on the Manufacture of Ordnance, 1886, no gun is 
allowed to be strained beyond three-fourths of the elastic 
limit of the material, which is fixed at 15 tons per square 
inch for the A tube, and 18 tons for hoops or the 
B tube. 

Consequently the allowed strain is 15 x = 11 '25 tons 
for the A tube, and 18 x f = 13 '50 tons for the B tube. 

98. Making use of the above dimensions, it will be found by 
the usual formula that the greatest permissible pressure is 
9 665 tons per square inch at 64 inches from muzzle, and 
6 983 tons per square inch at 32 inches from muzzle. 

99. Now, with the E.X.E. powder the pressures at these 
points are about 10 tons and 8 tons^per square inch respec- 
tively, so that the gun nearly answers to the required condi- 
tions; but with the B.N. powder the pressures would be 
14 tons and 10 tons per square inch respectively, an excess 
of 4 tons in the first case and about 3 tons in the second. 

100. It is therefore manifest that the strength of this gun 
in the chase is quite insufficient for a charge of 28 f 52 Ibs. of 
B.N. powder, and any less charge would give a less ballistic 
result. 

101. It may be objected that the dotted curve Fig. 4 is 
theoretical, and not based on actual observation, except as 
regards the maximum pressure, and that the actual results 
of firing have not shown the guns to be too weak. 

102. With regard to the last objection, it has not much 
weight. A gun may go on firing for a greater or less time 
without bursting or any visible damage, but not the less 
surely is it injured every time that it is strained beyond the 
elastic limit, and this seems to be fully admitted at Woolwich, 
where, as stated in the Official Treatise, the practice is to 
limit the maximum strain to three-fourths of the elastic 
limit. If, therefore, the present guns are not too strong for 
the present powder, and if the pressure curves be even 



SMOKELESS POWDER. 33 

approximately correct, the guns cannot safely be used with 
the new powder with increased ballistic effect. 

103. The objection against the curve as theoretical carries 
more weight. Not only is it theoretical, but it depends 
on the assumption of the pressure in a close vessel being 
78 * 52 tons per square inch. 

The reason for this assumption is given above, and there is 
nothing in it which appears either improbable or inconsistent 
with such other facts as are known with respect to this 
powder. 

The law of decrease of pressure by which the ordinates and 
the curves are calculated is a rational law, and in all pro- 
bability approximately true for the powder gases. 

104. Moreover, the velocities deduced from the area of 
these curves (due allowance being made for other resist- 
ances) agree very well with the observed velocities, and 
consequently, whatever be the real form of the pressure 
curve, its area must be approximately the same as that of the 
dotted curve, Fig. 4. 

105. In the next place, the final ordinate at the muzzle 
must be the same (if all the charge is consumed), but it is 
quite possible that the point of maximum pressure may be 
further to the rear than shown in the curve, Fig. 4. 

Indeed, the curve may possibly be of such a form as 
shown in Fig. 5, A B C, the area of which may be the same 
as that of A B t C. Even in this case the pressures in front 
of the chase must be greater than with the other powder. 

It may also be observed that, to permit of the possibility 
of a curve of the form ABC, the rate of the evolution of 
gas must be very different from anything previously known. 

106. There is another strain besides the bursting strain 
which must be provided for, viz. the longitudinal strain in 
the chase of the gun arising from the friction of the products 
of combustion rushing along the muzzle. 

107. The importance of this strain has never been recog- 
nised by gun-makers, nor do there appear to have been any 
experiments made to ascertain its magnitude. In ' Internal 

D 



34 SMOKELESS POWDER. 

Ballistics' reasons have been given for attributing to it a 
very considerable magnitude, and indeed there can be little 
doubt on the subject. 

108. To what extent the magnitude of this strain will be 
affected by the use of the new powder can only be conjec- 
tured. On the one hand, the volume, pressure, and tem- 
perature of products of combustion are considerably greater. 

FIG. 5. 




On the other hand, these products consist of nearly perfect 
gases, and the coefficient of friction will probably be less 
than in the mixture of gases and finely diffused liquid 
arising from the combustion of the old powders. 

109. The subject of the longitudinal strain is of such 
importance that it is inconceivable to the author that gun- 
makers have taken no steps to ascertain its magnitude and 
relation to the other ballistic elements. 



SMOKELESS POWDER. 35 



VI. 

INFLUENCE OF THE NEW POWDER ON THE DESIGN OF GUNS. 

110. It has been shown that no great improvement in 
ballistic effect can be looked for, consistent with safety, 
with the present guns and the new powder. It is, there- 
fore, proper to give some attention to the subject of a 
design of gun suitable for the development of the new 
explosive. 

111. Up to the present, the idea of gun-makers seems to 
be running in the old groove low pressure and length of 
gun. 

The French 15 cm. Q.F. Canet gun is called a gun of 
48 calibres, but that is the length over all. The real length 
is as follows : 

Chamber 50 inches -f chase 227-5 = 277 -5 inches. 

It is only slightly chambered, and the equivalent length of 
the chamber is 53 2 inches. The total capacity of the gun 
is 7674 cubic inches, and of the chamber 1500 cubic inches, 
so that it is a gun of 5 '116 expansions, that is to say, a very 
long gun. 

112. But long guns are very inconvenient and objectionable, 
especially at sea, and the question arises whether it would 
be practicable to take advantage of the new powder in a 
short gun, even though it were at the expense of decreasing 
the efficiency per pound of powder. 

113. The gun may be shortened in two ways : First, by 
an enlarged powder chamber, which, however, has the dis- 

D 2 



36 SMOKELESS POWDER. 

advantage of increasing the strain upon the breech apparatus ; 
or, secondly, by increasing the maximum working pressure. 

114. To what extent this may be done cannot at present 
be solved in a general form, inasmuch as the relations be- 
tween the ballistic effect of the new powder and the ballistic 
elements, such as calibre of gun, travel and weight of pro- 
jectile, and " characteristics " of the new powder are unknown 
in this country. 

115. Recourse must therefore be had to the method of 
curves, and to such limited information as is given in the 
published results contained in the first part of this paper. 
The question will therefore be confined to a gun resembling 
M. Canet's 15 cm. Q.F. gun with a calibre of 5*95 inches, 
and travel and weight of projectile 224-5 inches and 
89 Ibs. 

116. Suppose (what might be easily done) a wire gun to 
be made so as to give the same margin of safety under a 
pressure of 30 tons as the Canet gun under a pressure of 
18-81 tons. 

By the formula (2), P = 0172 w 2 , and making P = 30, we 
get w = 41 -76 Ibs., and consequently V = 198 wl = 3253 f.s. 
Let the capacity of the chamber be 45 5 cubic inches per Ib. 
of powder, which is the same gravimetric density as in the 
last round of the Canet gun. (See Table II.) 

The capacity of the chamber is 1500 cubic inches, and the 
equivalent length 53 inches, and the length of charge 
47 inches. 

With these data the curve Fig. 6 is constructed, the area 
of which is 301, which multiplied by the area of the pro- 
jectile 27-4, gives 8247 foot-tons. 

Deducting, as before, 20 per cent for resistances, expulsion 
of gases, &c., there remains 6595 foot-tons, which corresponds 
to a velocity of 3271 feet per inch, which is very nearly the 
velocity found by the formula V = 198 wl. 

117. The weight of this gun would probably be about 
7J- tons, for on the wire construction it could be made con- 
siderably lighter in proportion than the Canet gun. 



SMOKELESS POWDER. 37 

Therefore the relative efficiency of the two guns would be 







Energies. 


Description of Gun. 


Energy. 


Per Ton of 


Per Ib. of 






Gun. 


Powder. 


CanetQ.F 


4665 


744-6 


141 


Proposed gun 


6598 


910-1 


158 



Showing the decided advantage of the high-pressure gun. 

118. It may now be inquired, what would be the length of 
the proposed high-pressure gun which would have the same 
ballistic power as the Canet gun ? 

This may be approximately ascertained from the curve 
Fig. 6. 

The difference of energy imparted to the projectile is 
1933 foot- tons, to which must be added 20 per cent., making 

FIG. 6. 



30 



10- 



t S3.. 

c 47'- i 

KBH 

41. 76 Ws 



> 102' 

224.5 



2320 foot-tons, which divided by the area 27 * 4, gives 84 68 
foot-tons to be deducted from the muzzle end of the curve, 
and since the mean pressure near the muzzle is about 
10 tons per square inch, the length to be deducted is 
84-64 



10 



= 8*46 feet or 103 inches, so that the travel of the 



projectile would be 122*5 inches and the total length of the 
gun over all, about 181 inches instead of 283 inches in the 
Canet gun. 



38. SMOKELESS POWDEE. 

119. The two guns would have the same ballistic power. 
The weights would be about the same, and the only difference 
would be the expenditure of 41f Ibs. of powder instead of 
33-081bs. 

120. With reference to the higher pressure proposed to be 
used it is to be observed that the maximum pressure in a gun 
depends not so much on the charge of powder as on Sarrau's 
characteristic a, or rather on a 2 , which is in his notation 

= - , in which/ is the " force " of the powder, a a coefficient 

T 

depending on the form of the grain, r the time of total com- 
bustion of the grain in free air. 

121. It is, therefore, obvious that with any given powder 
for which / has a fixed value, the value of a 2 may be 
modified by a corresponding modification of a and r, the first 
of which depends on the form of grain, the second on its 
density and least dimensions. 

It is, therefore, simply an object of research to make a 
powder of which the characteristics a, will give the required 
pressure. 

122. As is easily seen, the higher pressure is given by the 
lower value of r, whilst at the same time it may be effected 
by giving such a form to the grain as will give a higher 
value of a . 

The practical result of decreasing r is that the evolution 
of gas is quickened, and the pressure rises at an earlier 
period of the course of the projectile, because the projec- 
tile has not had time to move out of the way. 

123. It is, therefore, evident that the question of the deter- 
mination of the " characteristics " of these new powders, and 
the size and form of grain suited to the different calibres 
of guns, is one of first-rate importance, and without which 
future ballistic progress must be a matter of hap-hazard 
and danger. 



SMOKELESS POWDER. 39 



VII. 

CONCLUSION. 

124. Whilst the superiority of the new powder is incontes- 
table, there is a danger that must be guarded against. The 
very fact of its being a more powerful agent renders 
precaution in its use the more necessary. 

125. Its enormous " force " may be practically mitigated in 
two ways first, by the size and density of the grain, which 
governs the rate of evolution of gas, and secondly, by a 
low gravimetric density such as has hitherto been used. 
By a due adaptation of these, the rate of evolution of the 
gas has been so proportioned to the space behind the pro- 
jectile, that the pressures have been kept down to the 
moderate limit which the new type guns can resist ; but if 
by any cause, such as a change of constitution of the powder 
under great variations of climate, or by breaking up of the 
grains during transport, the rate of evolution of gas is sud- 
denly increased, then the very high " potential " of the 
powder may give rise to sudden abnormal increase of pressure, 
which the guns may be quite unable to resist, and serious 
accidents may occur. 

126. These new powders are certainly more liable to 
such changes of composition than the old powders, which 
are simply mechanical mixtures, and therefore it is the 
more necessary that the guns should be strengthened to the 
utmost, rather than fined down to meet the requirements of 
anticipated low pressures. 

127. The general conclusions which may be drawn from 
the preceding remarks are as follows : 

(1) That the smokeless powder has ballistic properties far 
superior to the old powders. 



40 SMOKELESS POWDER. 

(2) That the erosive action on the guns will probably be 
less. 

(3) That its use in existing guns of the new forged steel 
type will not lead to any considerable increase of ballistic 
effect without considerable risk, owing to the increase of 
pressure developed in the front part of the chase, although 
the actual maximum pressure on the gun may be less. 

(4) That to utilise the high ballistic powers of the new 
powders very strong guns will be required, and that such 
guns will have to be much stronger in front of the trunnions 
than those of the new type forged steel guns. 

That to arrive at very high ballistic results it is not 
necessary to have guns of inordinate length, but by the 
adoption of higher initial, instead of low and more uniform 
pressures, velocities of 3000 feet per second and upwards are 
attainable with perfect safety. 

128. In bringing these remarks to a conclusion, the author 
may perhaps be allowed to give expression to opinions, which 
in his own mind amount to convictions, as to the future of 
gun construction and ballistic effects. 

129. The first of these is, that low maximum pressure is a 
mistake. It has no raison d'etre except the weakness of the 
gun. It involves a length of gun which for naval use k is 
most objectionable. No doubt M. Canet has achieved very 
brilliant results with his 15 cm. Q.F. gun, but this gun is 
23 feet 4 inches in length over all. A " similar " gun 
of 12 inch calibre would be about 46 feet 8 inches long. 
" Similarly " loaded it would fire a charge of B.N. powder 
of 264 Ibs., and a projectile of 712 Ibs., with a muzzle velocity 
of 2750 . feet per second, giving a muzzle energy of 37,330 
foot-tons, or 848 3 foot-tons per inch of circumference. 

Now, as was shown in ( 118), a 15 cm. gun of equal power, 
firing with a maximum pressure of 30 tons per square inch, 
would be 15 feet long, and a " similar " gun of 12 inch calibre 
would be 30 feet long, as against 46 feet 8 inches for the 
low pressure gun. There can be no doubt which gun is the 
most suitable for naval service. 



SMOKELESS POWDER. 41 

130. A second conviction is, that guns of a very large 
calibre are a further mistake, and the author ventures to 
think that a 9-inch or 10-inch high pressure gun would be 
sufficient for any effect that is required against the heaviest 
armour afloat. 

131. A third conviction is, that in order to utilise the new 
powders recourse must be had to the wire system of con- 
struction, by which alone guns of sufficient strength can be 
obtained. 

132. Lastly, he would express the opinion that no time 
should be lost in carrying out such a series of experiments 
as will enable formulae analogous to those of M. Sarrau to 
be constructed for these new powders, and also for the 
determination of the tensile strain on the chase caused by 
the friction of the products of combustion. 



( 42 ) 



APPENDIX A. 

DECOMPOSITION OF NOBEI/S POWDER AS A TYPE OF THE 
SMOKELESS POWDERS. 

According to Nobel's specification, No. 1471/88, 100 
grammes of powder contain 

Grammes. 

Nitroglycerine 23-10 

Nitrocellulose 23-10 

Perchloride ammonia 50*35 

Camphor 3-45 

After explosion these give rise to new products, viz. : 

From the Nitroglycerine. 

Grammes. 

Carbonic acid 13-435 

Nitrogen 4-275 

Oxygen -814 

Water 4-579 



Total .. .. 23-10 

From the Nitrocellulose. 

Grammes. 

Carbonic acid 10-670 

Carbonic oxide 6*791 

Hydrogen -343 

Nitrogen .. 3*112 

Water 2-183 

Total . 23-10 



APPENDIX A. 43 

From the Camphor. 

Grammes. 

Carbon 2-81 

Hydrogen 0-33 

Oxygen 0-38 

Total .. .. 3-47 

From the Perchloride of Ammonia. 

Grammes. 

Chlorine 16-63 

Oxygen 25-87 

Nitrogen 6-47 

Hydrogen .. .. 1-39 



Total .. .. 50-35 

. 

Certain of the products of the camphor and perchloride 
unite, and the final result of the decomposition is 

Grammes. 

Carbonic acid , 41-26 

Nitrogen 13-86 

Water 25-24 

Chlorine 16-64 

Oxygen 2-96 

Total . 100-00 



VOLUME OF GASEOUS PEODUCTS. 

The volume of the products in the last paragraph at 
Centigrade and * 76 metres of mercury would be 

Cub. Decimetres. 

Carbonic acid 20-87 

Nitrogen 11-04 

Watery vapour 31*31 

Chlorine .. 8-21 

Oxygen 2-08 

Total . 70-51 



44 APPENDIX A. 

Therefore, from 1 gramme of powder the volume of gas 
= *7051 cubic decimetres, or 705*1 cubic centimetres. 

In the above the water has been considered as in the state 
of a permanent vapour, though of course that is impossible at 
Centigrade, but as forming part of the products of com- 
bustion it is always in the gaseous form, and may therefore 
properly be comprised among the gaseous products, proper 
allowance being of course made when the evolution of heat 
is considered, for the heat absorbed in the vaporisation of 
the water. 

HEAT EVOLVED PER GKAMME OF POWDER. 

Keverting to the 100 grammes of powder, the heat evolved 
is that evolved in the formation of 42 26 grammes of car- 
bonic acid and 25 24 grammes of water. The first contains 
11-25 grammes of carbon, and the second 2 '80 grammes of 
hydrogen. 

Consequently the heat evolved is 

From Carbon .. 11-25 x 8-08= 90 9 units Centigrade. 
Hydrogen 2-80x34-46= 96-5 

Total .. .. 187-4 

but the heat required to vaporise 25 '4 grammes of water is 
25-4 x '631 = 15-92 units Centigrade. 

Deducting which there remains 171-48 units, or for 
1 gramme of powder 1*7148 units Centigrade. 



TEMPERATURE OF PRODUCTS. 

This can only be given as a comparison with other 
powders, and not as the real temperature existing in the 
gun under circumstances when the loss of temperature due to 
cooling and the specific heat at very high pressure and tem- 
perature are both unknown. 



APPENDIX A. 45 

The temperature now in question is what might be called 
the potential temperature or the theoretic temperature, and 
is calculated on the assumption that there is no loss by 
cooling, and that the specific heat remains constant. 

Under these conditions it may be compared with the 
potential or theoretic temperature of ordinary powders. 

NOBEL'S POWDER. MEAN SPECIFIC HEAT OP PRODUCTS. 

Carbonic acid .. .. 41-26 x '172 = 7-097 

Nitrogen 13-86 x '173 = 2-398 

Watery vapour .. .. 25-40 x '337 = 8-506 

Chlorine 16-64 x '086 = 1-431 

Oxygen 2-96 x '155 = 0-459 



100-00 19-891 

Therefore the mean specific heat = 199. 

TEMPERATURE. 

Since the heat evolved is 1*7148 units per gramme, or 
1714 * 8 units per kilogramme, the temperature will be 

1714-8 

-- = 8673 C. 



( 46 ) 



APPENDIX B. 

In order to compare with the Nobel powder, Pebble powder 
is taken as a type of the old powders, and its composition, as 
given by Noble and Abel in their * Kesearches on Explosives ' 
(' Trans. Koyal Society/ 1880), is 

Parts. 

Saltpetre -7467 

Sulphate (sic) -0009 

Sulphur -1007 

Carbon -1212 

Hydrogen .. -0042 

Oxygen '0145 

Ash -0023 

Water -0095 

1-0000 

And the products of combustion of 1 gramme at Cent, 
and * 76 metres of mercury 

Grammes. Vols. in cm. 3 

Carbonic acid -2627 .. 132-9 

Carbonic oxide '0468 .. 37-1 

Nitrogen.. .. '1099 .. 87-5 

Sulphydric acid -0109 .. 9'2 

Marsh gas .. '0006 .. 0-8 

Hydrogen -0006 .; 6-7 

Watery vapour '0006 .. 11-7 

4410 285-9 

The remaining products consist of about 56 gramme of 
salts, chiefly of potassium and sulphur, which whilst in the 
gim are in the form of a liquid diffused throughout the gases 
and at the same temperature. 



APPENDIX B. 47 

HEAT EVOLVED. 

The heat evolved from 1 gramme of powder is that due to 
the combustion of the carbon and hydrogen in it. 
The carbon is as follows : 

Grammes. 

From Carbonic acid .. -2627 X A = '0717 
Carbonic oxide .. -0468 X -& = '0201 
Marsh gas .. .. -0006 x f = -0005 

Total 0-0923 

The hydrogen is 

In Sulphydric acid .. .. -0109 x T V = '00063 

Marsh gas -0006 X | = '00009 

Water -0006 X i = -00006 

-0095 X i = '00106 

Total -00184 

Consequently the heat evolved is 

Units. 

From Carbon to Carbonic acid .. -0717 x 8-08 =0-5793 
Carbonic oxide .. -0201x2-473= -0497 
Marsh gas .. .. -0005 x 8-08 = -0041 
Hydrogen -00184 X34-46 = -0634 



6965 

From this must be deducted the heat required to vaporise 
the water, or 

0101 x -631 = -0063 



Total -6902 

MEAN SPECIFIC HEAT. 
This is given by Noble and Abel as 187. 

TEMPERATURE (POTENTIAL OR THEORETIC). 
The heat evolved from 1 kilogramme is 690 '2 units, 
therefore temperature -7537" == 3690 Cent. 



APPENDIX C. 

VELOCITY AND PRESSURE IN 5-905 INCH Q.F. CANET GUN WITH 
54 LBS. P. POWDER. 

Ballistic Elements. 



c 


I 


w 


W 


A 


Log o )8~ 


Log o a 


5-905 


224-5 


54 


89 


1 


23014 


43223 



FORMULA FOR VELOCITY. (' Internal Ballistics, p. 137.) 



V = 


= m a p - 7 

W^ 


; tnereiore 


FORMULA 


FOR PRESSURE : 


P = Ka*A(^y 

\ c 2 / 


logM 


2-84567 


logK = -61174 


>, * F* = 


23014 


a 2 = -43223 


,J W* = 


64963 


A = -00000 


A^ = 


00000 


W^= -97470 


c* = 


09640 


w^ = -86619 


-* - 


44055 







Deduct 




logV =3-40988 
.-. V = 2570 f. s. 



2-88486 
Deduct 

logc 2 = 1-54249 

logP =1-34237 
.-. P = 22-00 



POSTSCRIPT. 



WHILST the above pages were passing through the press 
I have read an interesting article, in the* United Service 
Magazine ' of August 1890, by Professor Lewes, of the Eoyal 
Naval College, on "The Present State of the Powder 
Question." Agreeing generally in the Professor's con- 
clusions, I must take exception to one or two of his remarks. 
I do not agree that a perfect powder is one of which the 
production of gas goes on until the projectile reaches the 
muzzle of the gun. Such a powder would be very wasteful, 
and would carry the region of high pressure much too far 
forward in the gun. 

Then, again, I think there must be some mistake in the 
diagram which is given as representing the pressures in the 
chase with the three powders P 2 , Bl. Prism, and Br. Cocoa. 
The areas of the three curves A, B, and C, if correct, must 
be proportional to the muzzle energies of the projectile. The 
velocities are proportional to the square roots of the re- 
spective energies, that is to say, to the square root of the 
areas of the curves. 

Now, these three curves are represented by the relative 
numbers 69 * 5, 76, and 67 5, the square roots of which are 
8-33, 8 72, and 8 22, respectively. 

Consequently, assuming the velocity of 1608 feet per 
second to be correct for the P 2 powder, the other velocities 
as represented by the curves would be, Black Prismatic 
1683 feet, and Brown Cocoa 1586 feet per second, instead 
of 1708 and 1798 feet per second as given by Professor 
Lewes. It is therefore evident that there must be some 
mistake in the curves shown in the diagram. 

I am very glad to see that Professor Lewes insists strongly 
on the importance of the question of the stability of the 
new powders. 

H! 



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